/*
 * 版权所有 (C) 2015 知启蒙(ZHIQIM) 保留所有权利。[遇见知启蒙，邂逅框架梦，本文采用木兰宽松许可证第2版]
 * 
 * https://zhiqim.org/project/zhiqim_kit/zhiqim_git.htm
 *
 * ZhiqimGit is licensed under Mulan PSL v2.
 * You can use this software according to the terms and conditions of the Mulan PSL v2.
 * You may obtain a copy of Mulan PSL v2 at:
 *          http://license.coscl.org.cn/MulanPSL2
 * THIS SOFTWARE IS PROVIDED ON AN "AS IS" BASIS, WITHOUT WARRANTIES OF ANY KIND,
 * EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO NON-INFRINGEMENT,
 * MERCHANTABILITY OR FIT FOR A PARTICULAR PURPOSE.
 * See the Mulan PSL v2 for more details.
 */
package org.zhiqim.git.objer.loader;

import java.io.IOException;

import org.zhiqim.git.objer.ObjectLoader;
import org.zhiqim.git.objer.PackFile;


/**
 * 包对象加载器基类
 *
 * @version v1.0.0 @author zouzhigang 2017-3-30 新建与整理
 */
public abstract class PackedObjectLoader implements ObjectLoader
{
    protected int type;
    protected int size;
    protected byte[] data;
    
    protected final PackFile pack;
    protected final long dataOffset;
    protected final long objectOffset;

    PackedObjectLoader(PackFile pack, long dataOffset, long objectOffset)
    {
        this.pack = pack;
        this.dataOffset = dataOffset;
        this.objectOffset = objectOffset;
    }
    
    /***************************************************************************************/
    //子类必须实现的方法
    /***************************************************************************************/
    
    /**
     * 加载文件内容到内存中，当.getData()时调用，关闭PackFile
     * 
     * @throws IOException
     */
    protected abstract void load() throws IOException;

    /***************************************************************************************/
    //属性方法
    /***************************************************************************************/
    
    @Override
    public final int getType()
    {
        return type;
    }

    @Override
    public final long getSize()
    {
        return size;
    }

    @Override
    public final byte[] getData() throws IOException
    {
        if (data == null)
            load();
        
        return data;
    }

    public final long getObjectOffset()
    {
        return objectOffset;
    }

    public final long getDataOffset()
    {
        return dataOffset;
    }
}
